1. Field of the Invention
The present invention relates to an imaging device comprised of a base on which an imaging element is provided, a cylindrically shaped plastic lens member holding a condensing lens at the inside, and a plastic barrel member in which the lens member can move in the axial direction and provided on the imaging element, a method of production of the same, and an imaging device holding mechanism used for that production.
2. Description of the Related Art
With digital equipment being made more sophisticated in function and smaller in size, utilization of image recording functions has been increasing. Along with this, small sized camera components, that is, imaging devices, are increasingly being built into that equipment.
As such an imaging device, there is for example one of the configuration shown in FIGS. 9A and 9B. FIG. 9A is a perspective view, while FIG. 9B is a disassembled perspective view. In FIGS. 9A and 9B, a base 1 is provided with a cylindrical plastic barrel member 3. Inside the barrel member 3 and on the base 1 are provided a CCD, C-MOS sensor, or other imaging device 7. The inner circumference of the barrel member 3 is formed with a female thread 9.
The barrel member 3 is provided inside it with a plastic lens member 11. The lens member 11 is provided inside it with a condensing lens (not shown) for condensing light from a subject onto the imaging device 7. Further, the lens member 11 is formed at its bottom outer circumference with a male thread 13 able to engage with the female thread 9 of the barrel member 3.
To assemble an imaging device of such a configuration, first, the lens member 11 is inserted inside the barrel member 3, then the lens member 11 is turned to make the lens member 11 move in the axial direction of the barrel member 3 for focusing. After focusing, an adhesive is used to bond the barrel member 3 and the lens member 11 to thereby fix the condensing lens in place.
Further, when focusing by a lens other than the lens member 11, the following method has also been proposed. For example, unlike FIGS. 9A and 9B, a metal barrel member 3 with no female thread and a metal lens member 11 with no male thread 13 are used, the lens member 11 is inserted inside the barrel member 3, and the lens member 11 and barrel member 3 are affixed by calking (for example, see FIG. 10 and FIG. 11 of Japanese Unexamined Patent Publication (Kokai) No. 5-181043).
With the method of affixing the lens member 11 and the barrel member 3 by an adhesive, there are the following problems:                (1) The adhesive is coated after the focusing work. The device then has to be allowed to stand in a high temperature environment or an ultraviolet environment for tens of minutes to several hours or so of time for complete curing. Shrinkage of the adhesive results in deviation in the relative positions between the lens member 11 and the barrel member 3, so the focus ends up becoming off.        (2) The release of the residual stress remaining in the lens member 11 or the barrel member 3 from the time of forming the member (annealing effect) results in deformation of the entire member and distortion in the image.        (3) When the image obtained is poor, the lens member 11 is detached once from the barrel member 3, the focusing is performed again, then the members are bonded as a repair method. With this method, after detaching the lens member 11 from the barrel member 3 (hereinafter referred to as “reworking”), sometimes the adhesive, a material different from the base materials, remains at the surface of the lens member 11 or barrel member 3 resulting in poor bonding at the time of rebonding.        
Next, with the method of affixing the lens member 11 and the barrel member 3 by calking, there are the following problems:                (1) A large force acts on the lens at the time of calking, so the lens deforms or is damaged.        (2) A separate lens is required for focusing, so the cost becomes higher.        